Horton

Re: backup manifests

David Steele <david@pgmasters.net>

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From: David Steele <david@pgmasters.net>
To: Robert Haas <robertmhaas@gmail.com>
Cc: "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2019-09-20T03:10:46Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Try to avoid compiler warnings in optimized builds.

  2. Fix option related issues in pg_verifybackup.

  3. Add index term for backup manifest in documentation.

  4. Code review for backup manifest.

  5. Document the backup manifest file format.

  6. Fix typo in pg_validatebackup documentation.

  7. Exclude backup_manifest file that existed in database, from BASE_BACKUP.

  8. Msys2 tweaks for pg_validatebackup corruption test

  9. Fix resource management bug with replication=database.

  10. Be more careful about time_t vs. pg_time_t in basebackup.c.

  11. pg_validatebackup: Fix 'make clean' to remove tmp_check.

  12. pg_validatebackup: Also use perl2host in TAP tests.

  13. Generate backup manifests for base backups, and validate them.

  14. Add checksum helper functions.

  15. pg_waldump: Add a --quiet option.

  16. Catversion bump for b9b408c48724

  17. pg_basebackup: Refactor code for reading COPY and tar data.

  18. Use a ResourceOwner to track buffer pins in all cases.

  19. Use ARMv8 CRC instructions where available.

  20. Logical replication support for initial data copy

  21. Use Intel SSE 4.2 CRC instructions where available.

  22. Switch to CRC-32C in WAL and other places.

  23. Remove support for 64-bit CRC.

  24. Change CRCs in WAL records from 64bit to 32bit for performance reasons.

On 9/19/19 11:00 AM, Robert Haas wrote:

> On Thu, Sep 19, 2019 at 9:51 AM Robert Haas <robertmhaas@gmail.com> wrote:
>> I intend that we should be able to support incremental backups based
>> either on a previous full backup or based on a previous incremental
>> backup. I am not aware of a technical reason why we need to identify
>> the specific backup that must be used. If incremental backup B is
>> taken based on a pre-existing backup A, then I think that B can be
>> restored using either A or *any other backup taken after A and before
>> B*. In the normal case, there probably wouldn't be any such backup,
>> but AFAICS the start-LSNs are a sufficient cross-check that the chosen
>> base backup is legal.
> 
> Scratch that: there can be overlapping backups, so you have to
> cross-check both start and stop LSNs.

Overall we have found it's much simpler to label each backup and 
cross-check that against the pg version and system id.  Start LSN is 
pretty unique, but backup labels work really well and are more widely 
understood.

>>>> (3) Cross-check a manifest against a backup and complain about extra
>>>> files, missing files, size differences, or checksum mismatches.
>>>
>>> Verification is the best part of the manifest.  Plus, you can do
>>> verification pretty cheaply on restore.  We also restore pg_control last
>>> so clusters that have a restore error won't start.
>>
>> There's no "restore" operation here, really. A backup taken by
>> pg_basebackup can be "restored" by copying the whole thing, but it can
>> also be used just where it is. If we were going to build something
>> into some in-core tool to copy backups around, this would be a smart
>> way to implement said tool, but I'm not planning on that myself.
> 
> Scratch that: incremental backups need a restore tool, so we can use
> this technique there. And it can work for full backups too, because
> why not?

Agreed, once we have a restore tool, use it for everything.

-- 
-David
david@pgmasters.net